Chromosomal features and evolution of Bromeliaceae

New cytological information and chromosome counts are presented for 19 taxa of 15 genera of the Bromeliaceae, among them, data for 15 taxa and five genera are reported for the first time. The basic number x = 25 is confirmed and polyploidy seems to be the main evolutionary mechanism in Bromeliaceae. Most of the analyzed species presented 2n = 50. Polyploids have been detected in Deinacanthon urbanianum with 2n = ca.160 and Bromelia laciniosa with 2n = ca.150. In Deuterocohnia lorentziana we observed individuals with two different ploidy levels (2n = 50 and 2n = 100) growing together in the same pot. Ayensua uaipanensis showed the uncommon number 2n = 46. After triple staining with CMA₃/Actinomycin/DAPI one or two CMA⁺/DAPI⁻ bands could be observed in the studied species (Aechmea bromeliifolia, Greigia sphacelata and Ochagavia litoralis). The role of these features in the evolution of the family is discussed, revealing new aspects of the evolution of the Bromeliaceae.     

Chromosome numbers and DNA content in Bromeliaceae: additional data and critical review

For the large Neotropical plant family Bromeliaceae, we provide new data on chromosome numbers, cytological features and genome size estimations, and combine them with data available in the literature. Root‐tip chromosome counts for 46 species representing four subfamilies and a literature review of previously published data were carried out. Propidium iodide staining and flow cytometry were used to estimate absolute genome sizes in five subfamilies of Bromeliaceae, sampling 28 species. Most species were diploid with 2n = 50 in Bromelioideae, Puyoideae and Pitcairnioideae, followed by 2n = 48 observed mainly in Tillandsioideae. Individual chromosome sizes varied more than tenfold, with the largest chromosomes observed in Tillandsioideae and the smallest in Bromelioideae. Genome sizes (2C‐values) varied from 0.85 to 2.23 pg, with the largest genomes in Tillandsioideae. Genome evolution in Bromeliaceae relies on two main mechanisms: polyploidy and dysploidy. With the exception of Tillandsioideae, polyploidy is positively correlated with genome size. Dysploidy is suggested as the mechanism responsible for the generation of the derived chromosome numbers, such as 2n = 32/34 or 2n = 48. The occurrence of B chromosomes in the dysploid genus Cryptanthus suggests ongoing speciation processes closely associated with chromosome rearrangements. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 176 , 349–368.     

凤仙花近缘种间核型分析与叶表皮微形态研究

为探究凤仙花近缘种植物的细胞学和微形态学方面的亲缘关系,该文选取荔波凤仙花(Impatiens liboensis)及近缘种赤水凤仙花(I.chishuiensis)和管茎凤仙花(I.tubulosa)的根尖和叶表皮为实验材料,采用体细胞染色体常规压片法和叶表皮光学显微镜观察法对凤仙花近缘种植物进行染色体及叶表皮特征研...     

Contribution to the cytotaxonomy of Oryzopsis (Poaceae)

Meiotic studies were performed in twelve populations of four Oryzopsis species (O. pubiflora, O. lateralis, O. holciformis var. longiglomis and O. barbellata) to obtain data on the ploidy level and cytological evolution of the genus. The chromosome number 2n=2x=24 was revealed in all the species and populations studied. The present and other studies show the occurrence of two basic chromosome numbers in the genus, i.e. x=11 and x=12. Although Oryzopsis species and populations studied are diploid and are expected to form only bivalents in metaphase of meiosis‐I, quadrivalents were observed in O. pubiflora and O. lateralis, possibly due to the occurrence of heterozygote translocations. B‐chromosomes of 0–2 were observed in all species and populations studied. This is the first report of the occurrence of B‐chromosomes in the genus Oryzopsis. Several meiocytes showed the presence of double chromosome number in O. lateralis, and multipolar cells were observed in populations of O. barbellata, O. lateralis and O. holciformis var. longiglomis. The occurrence of large pollen grains (possibly unreduced) was observed along with smaller (normal) pollen grains in these species. Significant differences observed in chiasma frequency and distribution among studied species may be of use in species delimitation. The Kakan population differed significantly from the other populations of O. lateralis in meiotic characteristics. If such cytological differences are accompanied by morphological variation (under investigation), we may consider this population as a new variety or subspecies.     

Study of the mitotic and meiotic chromosomes of sotol (<i>Dasylirion cedrosanum</i> Trel.)

The genus Dasylirion is a group of plants typically present in the Chihuahuan Desert, perennial, with a dioecious sexual behavior and commonly called sotoles. This genus has been little studied from the biological point of view, and the bases of its reproductive response remain unknown. In this work we studied the chromosome number and meiotic response of Dasylirion cedrosanum in the county of Saltillo, Coahuila, located at the North East of Mexico. For the preparation of mitotic chromosomes, we used a technique based on enzymatic treatment with pectolyase and cellulase, as well as staining with acetocarmin dye. For the study of meiosis, male flower buds were collected, fixed and stained for analysis with the same dye. As a result, the gametic (n = x = 19) and somatic chromosome (2n = 38) numbers of D. cedrosanum are reported for the first time, being consistent with previous findings in other Dasylirion species, which points to a constant ploidy level across the genus. Variation was observed in the morphology and size of the somatic chromosomes, with types ranging from submetacentric to subtelocentric, and sizes oscillating in a range of 4.43 µm, with an average total length of 112.38 µm for the diploid chromosome complement. This shows that the chromosome complement of D. cedrosanom would belong to a 3B classification of Stebins, with a medium variation between chromosome lengths and low chromosome asymmetry. This variation indicates the feasibility of constructing a chromosome ideotype for this species. The meiotic chromosome pairing showed a chromosome behavior consistent with a disomic inheritance characteristic of a diploid species, with prevalence of ring and chain bivalents, typically without pairing abnormalities. Bivalent configurations in all cases were symmetrical.The normal and symmetrical meiotic pairing indicates a balanced production of gametes, and suggests the absence of heteromorphic sex determination.     

Phylogenetic studies of the genus <Emphasis Type="Italic">Cebus</Emphasis>(Cebidae-Primates) using chromosome painting and G-banding

Background  

Chromosomal painting, using whole chromosome probes from humans and Saguinus oedipus, was used to establish karyotypic divergence among species of the genus Cebus, including C. olivaceus, C. albifrons, C. apella robustus and C. apella paraguayanus. Cytogenetic studies suggested that the species of this genus have conservative karyotypes, with diploid numbers ranging from 2n = 52 to 2n = 54.     

Karyotype studies in thirty‐two species of Lilium (Liliaceae) from China1

Fifty‐two populations representing thirty‐two taxa of Lilium L. from China are karyologically analyzed. The results showed that all populations have the same basic chromosome number x=12, and all species are diploid except Lilium tigrinum, which is triploid with 2n=36. In addition, one population of L. sulphureum is aneuploid with 2n=23. The karyotype evolution in the genus Lilium is mainly in terms of alterations of the fine structure of the chromosomes, not in ploidy or basic chromosome number variation. When combining previous studies and our results, we consider the major driving forces for evolution of Lilium to be an increase in karyotypic asymmetry, and unequal translocation and formation of secondary constrictions. The existence of intercalary satellites on the two largest pairs of chromosomes is correlated with the geographic distribution pattern of Lilium across the world. The Hengduan Mountains is a modern diversity and differentiation center of Lilium and it also could be the center of origin for this genus. In addition, some taxonomic conclusions were verified on the subgenus level. Among the species investigated, the chromosome number and karyotypes of 13 taxa were documented for the first time.     

Cytotaxonomy of Dubyaea glaucescens (Compositae–Cichorieae)

Recent molecular phylogenetic analyses indicate that Dubyaea glaucescens (Compositae–Cichorieae) should be transferred to the genus Faberia as F. glaucescens. Here, we present cytological evidence for this transfer. Dubyaea glaucescens comprises two ploidy levels, 2n = 34 (diploid) and 2n = 51 (triploid), making the basic chromosome number x = 17. The chromosomes vary in length from 5.82 μm to 2.11 μm, and the karyotypes are 2n = 20m + 14sm (3sat) for the diploid cytotype and 2n = 30m + 21sm (3sat) for the triploid cytotype. Karyological characters of D. glaucescens, including chromosome number, size, morphology, and karyotype asymmetry, all agree remarkably with those reported previously in Faberia, but are distinct from those in other species of Dubyaea. The transfer of D. glaucescens to Faberia is thus strongly corroborated.     

半蒴苣苔属植物染色体制片优化及染色体数目和倍性研究

染色体数目和倍性是系统与进化生物学和遗传学研究中十分重要的基础信息。为探索半蒴苣苔属染色体制片的适宜条件以及染色体数目的进化模式及其与物种的进化关系，该研究基于半蒴苣苔属染色体数目的进化历史，并根据该属植物具有叶片扦插繁殖的特性，采用叶片水培生根法获取半蒴苣苔(Hemiboea subcapitata)、弄岗半蒴苣苔(H.longgangensis)、龙州半蒴苣苔(H.longzhouensis)、江西半蒴苣苔(H.subacaulis var.jiangxiensis)、华南半蒴苣苔(H.follicularis)和永福半蒴苣苔(H.yongfuensis)6种植物的根尖材料，分析不同实验条件对染色体制片效果的影响，对染色体制片实验的条件进行优化及染色体计数，结果表明：(1)9:30—10:00取材，解离10 min以及染色15 min为半蒴苣苔属染色体制片的适宜条件。(2)上述6种半蒴苣苔属植物均为二倍体，染色体数目均为32(2n=2x=32)。(3)除个别物种染色体数目有变化以外，该属大部分物种染色体数目可能为2n=2x=32且染色体数目变化可能是非整倍化的作用，与物种进化没有明...     

Photosynthetic characteristics in <Emphasis Type="Italic">Oryza</Emphasis> species

Photosynthetic rate (P _N), SPAD value, specific leaf area (SLA), flag leaf area (FLA), and nitrogen content (LN) of genus Oryza were investigated and their correlation was analyzed to assess some of the main photosynthetic traits among different species in the genus Oryza. The results revealed wide variation in these traits. The species O. rufipogon and O. australiensis exhibited maximum photosynthetic rate. Comparison of different types of genomes (diploid: 2n=2x=24; tetraploid: 2n=4x=48) and growth habit (shade- or sun-grown) showed the species of diploid (with genome symbol EE; 2n=2x=24) genomes, with perennial and sun-grown species, had high apparent photosynthesis compared to others. The species with BB/BBCC, shade-grown and the tetraploids showed high SPAD value, and the flag leaf in sun-grown species and diploids were thicker (low SLA) compared with others. However, no significant difference could be noticed among the different types of genomes. Higher leaf area was noticed among the species of CC/CCDD genome, perennial shade-grown species and tetraploids than in others. The variety IR 36 exhibited highest leaf nitrogen concentration. Correlation analysis showed a strong relationship between P _N and leaf nitrogen concentration while no marked relationships were observed among other characteristics. It implies that the species with thick and small leaves with high nitrogen concentration and high photosynthesis evolved better than others. O. rufipogon, with the same genome as O. sativa, could be one of the wild rice resources for elite crop improvement.     

New or rare data on chromosome numbers in several taxa of the genus<Emphasis Type="Italic">Artemisia (Asteraceae)</Emphasis> in Poland

Chromosome counts in 16 populations of fiveArtemisia species from Poland are presented in this paper. Those ofA. annua (2n=18) andA. dracunculus (2n=90) are reported for the first time in Polish populations. The decaploid level (2n=90) is described for the first time in non-cultivated populations ofA. dracunculus, and several cases of aneusomaty (intraindividual aneuploid variations in chromosome number: 2n=87, 88 and 89) have been detected in this species. In addition to the already known diploid number (2n=18), the tetraploid level (2n=36) has been detected inA. absinthium. The same two numbers have been recorded inA. abrotanum, which represents the first tetraploid count in populations of this taxon occurring outside botanical gardens. Finally, the chromosome number ofArtemisia campestris subsp.sericea (tetraploid, 2n=36) is reported for the first time. The relevance of polyploidy for the evolution of the genus and other cytotaxonomic or cytobiogeographical aspects are briefly discussed.     

Karyotype and genome size variation in Ajuga L. (Ajugoideae–Lamiaceae)

Chromosome number changes and karyotype evolution play an important role in plant genome diversification and eventually in speciation. The genus Ajuga L. (Lamiaceae) has approximately 50 species distributed in temperate to subtropical regions. Four of these species are currently recognized in Korea (A. decumbens Thunb., A. multiflora Bunge, A. nipponensis Makino and A. spectabilis Nakai). Understanding the karyotype evolution in Ajuga has been hampered by the small size of their chromosomes and symmetrical karyotypes. Here we used classic Feulgen staining to establish chromosome numbers and construct karyotypes of the four species of Ajuga recognized in Korea and flow cytometry was used to study their variation in genome. The chromosome number of all investigated plants was 2n = 32. Still, the 2C DNA content ranged from 2.18 pg (A. decumbens) to 4.53 pg (A. multiflora). While the chromosome numbers were the same for all investigated species, the genome size variation could potentially be used as a taxonomic marker.     

Island species radiation and karyotypic stasis in <Emphasis Type="Italic">Pachycladon</Emphasis>allopolyploids

Background  

Pachycladon (Brassicaceae, tribe Camelineae) is a monophyletic genus of ten morphologically and ecogeographically differentiated, and presumably allopolyploid species occurring in the South Island of New Zealand and in Tasmania. All Pachycladon species possess ten chromosome pairs (2n = 20). The feasibility of comparative chromosome painting (CCP) in crucifer species allows the origin and genome evolution in this genus to be elucidated. We focus on the origin and genome evolution of Pachycladon as well as on its genomic relationship to other crucifer species, particularly to the allopolyploid Australian Camelineae taxa. As species radiation on islands is usually characterized by chromosomal stasis, i.e. uniformity of chromosome numbers/ploidy levels, the role of major karyotypic reshuffling during the island adaptive and species radiation in Pachycladon is investigated through whole-genome CCP analysis.     

Karyotype characterisation of Brazilian species of the genus <Emphasis Type="Italic">Psychotria</Emphasis> L. — subfamily Rubioideae (Rubiaceae)

The pantropical genus Psychotria L., probably the largest among angiosperms, occurs in different Brazilian vegetal formations. This work determined the chromosome numbers and karyotypic characteristics of ten species of Brazilian Psychotria. The chromosome numbers ranged from 2n = 22, in five species (P. hoffmannseggiana (Willd. ex Roem. & Schult.) Müll. Arg., P. lupulina Benth., P. marginata Sw., P. tenerior (Cham.) Müll. Arg., and P. trichophora Müll. Arg.), to 2n = 40, in P. mapourioides DC., and 2n = 44 in four other species (P. carthagenensis Jacq., P. gracilenta Müll. Arg., P. longipes Müll. Arg. and P. suterella Müll. Arg.). In addition to these differences, great variations in chromosome lengths and karyotypic formulae were also observed among these species. Chromosome length varied from 5.59 μm to 0.90 μm and no relationship was detected between chromosome numbers and lengths in any species. Chromosomes are principally metacentric, except for P. mapourioides that presents mainly submetacentric chromosomes. Karyotypic asymmetry rate (TF%) ranged from moderate (TF% = 38.83) to highly symmetric (TF% = 50.00). The difference in chromosome numbers of Psychotria carthagenensis (2n = 44) and P. mapourioides (2n = 40) is very important to taxonomists, because these have great difficulty in identifying and differentiating these two species with the sole use of morphological characteristics, since some individuals have intermediate characteristics between both species. Although this study does not allow for a consistent cytotaxonomic analysis, not even to delimit P. subgen. Psychotria and P. subgen. Heteropsychotria, this karyotype analysis of some Brazilian species, along with their morphology, may contribute to a better knowledge of the genus.     

Genome size variation and species relationships in the genus Hydrangea

Genome size and base composition in 16 species and subspecies of the Hydrangea, a woody ornamental genus of Hydrangeaceae, were evaluated by flow cytometry in relation to their chromosome number. This is the first such study concerning the genome size of these species together with a karyotype study of the most important species, Hydrangea macrophylla subsp. macrophylla (Hortensia), from an economical point of view. The 2C DNA content ranged from 1.95 pg in Hydrangea quercifolia to 5.00 pg in Hydrangea involucrata. The base composition ranged from 39.9% GC in Hydrangea aspera subsp. sargentiana to 41.1% in Hydrangea scandens subsp. scandens (significant difference at p < 0.05). The smallest genome sizes were those of the three species originating from North or South America. Most of the species studied presented a chromosome number of 2n = 2x = 36, except for those of the section Aspereae which showed 2n = 30, 34 and 36. A primary karyotype has been made for the first time for H. macrophylla subsp. macrophylla. Phylogenetic relationships between species, the origin of chromosome number and an exploration of the genetic diversity within the genus are discussed. Received: 24 July 2000 / Accepted: 31 October 2000     

Chromosomes of Asian cyprinid fishes: Variable karyotype patterns and evolutionary trends in the genus Osteochilus (Cyprinidae, Labeoninae, “Osteochilini”)

The Cyprinidae family is a highly diversified but demonstrably monophyletic lineage of cypriniform fishes. Among them, the genus Osteochilus contains 35 recognized valid species distributed from India, throughout Myanmar, Laos, Thailand, Malaysia, Indonesian archipelago to southern China. In this study, karyotypes and other chromosomal characteristics of five Osteochilus species occurring in Thailand, namely O. lini, O. melanopleura, O. microcephalus, O. vittatus and O. waandersii were examined using conventional and molecular cytogenetic protocols. Our results showed they possessed diploid chromosome number (2n) invariably 2n = 50, but the ratio of uni- and bi-armed chromosomes was highly variable among their karyotypes, indicating extensive chromosomal rearrangements. Only one chromosome pair bearing 5S rDNA sites occurred in most species, except O. melanopleura, where two sites were detected. In contrast, only one chromosomal pair bearing 18S rDNA sites were observed among their karyotypes, but in different positions. These cytogenetic patterns indicated that the cytogenomic divergence patterns of these Osteochilus species were largely corresponding to the inferred phylogenetic tree. Similarly, different patterns of the distributions of rDNAs and microsatellites across genomes of examined species as well as their different karyotype structures indicated significant evolutionary differentiation of Osteochilus genomes.     

Does polyploidy occur in central European species of the family Sphaeriidae (Mollusca: Bivalvia)?

Some representatives of the bivalve family Sphaeriidae are assumed to be polyploid. In this study, 11 sphaeriid species (nine of the genus Pisidium, one of Musculium, and one of Sphaerium) inhabiting central Europe were studied karyologically, 10 of them for the first time. Analysis revealed high chromosome numbers (from 140 to 240). To elucidate the origin of high chromosome numbers, DNA contents were measured by flow cytometry in 5 of the studied species and, for comparison, in S. corneum and S. nucleus, which are known to be diploid (2n=30). Species with high chromosome counts yielded very similar DNA contents that are not higher than in the related species with low diploid numbers. This finding contradicts a possible origin of these species by recent polyploidization or hybridization of related species. Chromosome complements of the investigated species with high chromosome numbers differ from those with low 2n in their small chromosome size and the high proportion of subtelo- or acrocentric chromosomes. This indicates their possible origin either by an ancient polyplodization event followed by chromosomal rearrangements or by multiple chromosome fissions.     

CHROMOSOME NUMBERS IN CUPHEA (LYTHRACEAE): NEW COUNTS AND A SUMMARY

The American genus Cuphea with ca. 260 species is extremely diverse with respect to chromosome number. Counts are now available for 78 species and/or varieties, or 29% of the genus. Included in this study are first reports for 15 taxa from Brazil, Cuba, Dominican Republic, Mexico, and Venezuela. Twenty-two different numbers are known for the genus, ranging from n = 6 to n = 54. The most common number in the primary center of species diversity in Brazil is n = 8, which is regarded as the base number of the genus. Two numbers are most common in the secondary center in Mexico, n = 10 and n = 12. Species with n = 14 or higher are considered to be of polyploid origin. Polyploids comprise 46% of the total species counted and appear in 9 of the 11 sections for which chromosome numbers have been reported. Aneuploid species comprise ca. 25% of the genus and are known from 7 of the 11 sections. The two subgenera are not characterized by different chromosome numbers or sequences of numbers. None of the 14 sections are circumscribed by a single chromosome number. Morphological and ecological variability in widespread, weedy species is correlated with differing chromosome numbers in some species whereas in others the chromosome number is stable. Summary of chromosome numbers by taxonomic section is presented. Section Euandra, centered in eastern Brazil, and the largest section of the genus, appears to be chromosomally most diverse. In section Trispermum, characterized by difficult, variable species with intermediate forms, two of the four species studied have polyploid races. Section Heterodon, endemic to Mexico and Central America and comprising most of the annual species of the genus, is best known chromosomally. Chromosome numbers have been counted for 25 of 28 species, and 12 different numbers are reported. The most advanced sections, Melvilla and Diploptychia, with numerous species occurring at higher altitudes, are characterized by high polyploids. Apomictic species occur in sect. Diploptycia. The cytoevolution of Cuphea is complex with frequent polyploid and aneuploid events apparently playing a significant role in speciation in both centers of diversity.     

Karyotypic differentiation via 2n reduction and a finding of a case of triploidy in anurans of the genus <Emphasis Type="Italic">Engystomops</Emphasis> (Anura,Leiuperidae)

The genus Engystomops is divided into two groups, namely the Duovox clade and the Edentulus clade. The species of Edentulus clade have karyotypes with 2n = 22, while E. pustulatus and E. puyango, which belong to Duovox clade, have 2n = 20. To investigate if 2n = 20 is a synapomorphy of Duovox clade, we cytogenetically analyzed all the species of this group, except for E. puyango, in the present study. All of them had 2n = 20, differing from the species of Edentulus clade. Since the species already karyotyped of the genus Physalaemus, which is considered to be the sister group of Engystomops, also have 2n = 22, we conclude that the 2n reduction is a synapomorphy of Duovox clade. Despite the karyotypes of all the species of Duovox clade were very similar, they varied in the NOR pattern. In E. coloradorum, an additional NOR was found in one homologue of the chromosome pair 10 exclusively in all females, indicating that this could possibly be a sexual pair of the ZZ/ZW system. Also in this species, it was found the first case of natural polyploidy of the genus Engystomops.     

Karyology of the genus Faberia (Cichorieae–Asteraceae) and its systematic implications

Faberia Hemsl., a small genus of six species in the tribe Cichorieae, Asteraceae, has been karyologically investigated for the first time. All four studied species were revealed to have the somatic chromosome number 2n = 34, and thus the basic number of the genus was assumed to be x = 17. This rather high basic number has been previously reported very rarely in the tribe, occurring otherwise only in Warionia Benth. & Coss., a monospecific genus endemic to northwestern Africa, and in the American species of Lactuca L. The chromosome morphology was very similar among the four species, with the majority being median centromeric (m) and a few submedian centromeric (sm). In all the karyotypes the chromosomes were medium‐sized (6.33–1.61 μm), and showed a steady gradation in length from the longest to the shortest, with no evidence of bimodality. Our results strongly support the recognition of Faberia as an independent genus and the inclusion of Faberiopsis Shih & Y. L. Chen in Faberia.